Combination antiabrasion layer

ABSTRACT

A combination wear protection film for components made of substrates susceptible to wear is described. The film has a wear-resistant surface film that contains one or more of the elements carbon, nitrogen, or boron, the proportion of this element—or, if more than one of these elements is present, the sum of the proportions of the elements present—is at least 30% by atomic weight, preferably at least 40% by atomic weight; and a support film, located between a substrate and the surface film and made of a plasma polymer, that exhibits a quasi-continuous transition in modulus of elasticity and optionally in hardness from a value of a base film to a value of the surface film. A method for producing a wear protection film of this kind, and objects equipped with the wear protection film is also described.

FIELD OF THE INVENTION

The present invention relates to a combination wear protection film andmethods for generating and using the combination protection film intechnical devices, in particular mechanical energy transfer mechanisms.

BACKGROUND INFORMATION

Practically all objects are subjected to a greater or lesser degree ofwear due to interactions with their environment. As a rule, this wearresults over time and decreases in the utilitarian value orfunctionality of the object. Efforts have therefore always been made toconfigure technical components, i.e. objects having a technicalfunction, in such a way that when used as intended they exhibit aslittle wear as possible and thus can fulfill their purpose for as longas possible.

Depending on the manner in which they interact with their environment,components are subjected to very different wear stresses that are to becounteracted with very different measures.

In the case of components that do not need to transmit any appreciableenergy, wear occurs essentially due to the action of light, air,climatic influences, and/or particle impact. The principal task here isto equip the objects with nonporous, scratchproof surfaces. Oneconventional method that equipped a wide variety of surfaces withpolymer coatings is the plasma polymerization method. In this method, aplasma is generated by electrical excitation in a high vacuum usingsaturated or unsaturated compounds that can be vacuum-evaporated. Fromthe monomer compounds, fragments such as gaseous radicals, radical ions,ions, and excited molecules form in the plasma and are deposited onto asubstrate, on which they form a highly crosslinked polymer film thatconstitutes a sealed coating. Detailed information about implementationof this method is provided, for example, in Ullmanns Encyclopedia ofIndustrial Chemistry, Vol. A20, pages 755-756, 5^(th) ed. and theliterature cited therein, Comprehensive Polymer Science 4, pp. 357-375and Encyclopedia Polymer Science and Engineering. 11, pp. 248-261.

An interesting possibility, based on this method, for depositing atransparent scratchproof coating onto plastics such as polymethylmethacrylate or polycarbonate—as used, for example, in the manufactureof automobile headlights—is Schutzschichten durch Plasmapolymerisation(Protective Film Using Plasma Polymerization) of Bosch TechnischeBerichte (Bosch Technical Reports) 8 1986/87 published in HandbuchPlasmapolymerisation (Plasma Polymerization Manual), VDI-Bildungswerk(VDI Education Text), 1990. According to. this publication, plasmapolymerization of HMDS(O) is used to produce on the plastic surface aplasma polymer film that is relatively soft directly on the plasticsurface, but becomes harder and harder with increasing thickness andterminates in a hard, quartz-like surface film. In practical terms, thishardness gradient is produced by the fact that plasma polymerization isinitially performed in the presence of very little oxygen, and theoxygen partial pressure is continually raised as the film thicknessincreases.

Conditions are even more complex in mechanical energy transfer systems,which have components that are exposed not only to the kind ofmechanical stress that occurs in the case of headlight but also tolenses, for example stone impact, abrasion wear particularly high andcomplicated loads. Components of this kind are exposed to shear forces,impact stresses, high pressures, and in particular to sliding frictionalforces as well as long-term vibratory effects, which act on the elementseither individually or (as a rule) simultaneously, albeit to differentdegrees, and result in more or less rapid wear.

One solution that at first glance appears obvious—i.e. to manufactureall the functional elements from materials that can withstand thevarious wear stresses—runs into considerable and often insurmountabledifficulties, either because such materials are not conventional forsuitable materials are much too expensive or very difficult orimpossible to shape or machine into the desired components.

Many attempts have therefore been made to manufacture the functionalelements of mechanical energy transfer systems as well from easilyshaped and (whenever possible) also inexpensive materials, and to impartthe necessary wear resistance to them by way of a surface finish.

Different protective measures are necessary depending on the type ofeffect that causes the wear. It is conventional, for example, for drillsnot only to be equipped with hard metal cutting edges, but alsovacuum-coated with hard-material coatings, for example titanium nitride.In highly stressed energy transfer elements, however, very high demandsare placed on these surface protective coatings. Desirable propertiesinclude, for example, good adhesion to the component, good cohesion andminimal stress within the film, high hardness and load-carryingcapability, minimal coefficient of friction, good surface smoothness,and minimal adhesion to the countermember. In general, homogeneoushard-material films on wear-affected substrates cannot meet thisaforesaid combination of criteria. Methods have therefore already beendescribed for producing combination films that can be better adapted torequirements.

International Published Patent No. WO 95/16799 describes componentsequipped, for protection against wear, with a hard-material film that iscomposed of an adhesion film in contact with the component, a functionalfilm thereabove, and a surface film. The adhesion film comprises atitanium composition, in particular titanium boride, or, if thecomponent comprises a metallic substrate, pure titanium. The functionalfilm is made up in turn of three films of hard-material alloys (titaniumnitrides, titanium carbides, and/or titanium borides) of variouscomposition, for example titanium nitride, titanium carbonitride, andtitanium carbide, or titanium boronitride, titanium boronitride carbide,and titanium borocarbide, with gradual transitions in compositionbetween the films.

The individual films are obtained by successively vacuum evaporating thetitanium compositions, in accordance with a predetermined schedule, ontothe substrate while simultaneously allowing high-energy (and, inparticular, heavy) ions to act on it. The coating temperature for thismethod is approx. 200° C. The surface film comprises a metal-containingcarbon film (i-C(Ti)), and optionally also a metal-free carbon film(a-C:H) thereabove.

Film deposition in combination with heavy ion bombardment solvesadhesion and film separation problems.

For some time, efforts have been made to replace expensive and/ordifficult-to-machine materials with more favorable materials, e.g.roller bearing steel, for the manufacture of mechanically stressedcomponents. In the context of these efforts, many attempts have alsobeen made to fabricate components with a technical function fromplastics. Plastics not only have the advantage of economicalaccessibility, but are also available in many different types, can bemade into almost any desired shape, and have advantageous physicalproperties, e.g. favorable internal damping or resonance, which meansthey have little tendency to generate, accept and transmit vibration.This property not only prevents fatigue wear, but also results inparticular low operating noise.

In cases in which no appreciable mechanical loads occur, it has alsobeen possible to create sufficient surface protection, for example byapplying (as described above) a scratch protection film of SiO₂.

In the case of mechanically stressed components, however, the wearproperties of the more favorable materials are often inadequate. Asdiscussed above, in such cases an attempt is made to achieve thenecessary wear resistance for the components by way of a thin coating.In the case of plastics as an economical material for wear-stressedcomponents (i.e. gears or friction clutches), hard films must be appliedonto these components.

Since high-temperature tolerance plays a role in the coating process formany materials, and in particular for plastics, it is necessary to usecoating methods that are performed at relatively low temperatures and inwhich the film deposition rates are great. Many coating methods that areused for finishing metal surfaces are therefore unusable for coatingplastics.

It has been found that uniformly hard films are too brittle, and chipoff from plastic substrates in response even to the small pressurestresses that accompany most wear stresses (this behavior is called the“eggshell effect”). To get around this shortcoming, it is necessary tocreate a hardness gradient within the film; in other words, the filmhardness must be adjusted so that it gradually increases from theflexible plastic base to the hard surface film that is exposed to wear.This principle has been implemented in the aforementioned method,described in the Bosch Technical Reports, for coating plastics with atransparent SiO₂ scratch-protection film.

These conventional plasma polymer films with a hardness gradient havethe disadvantage of insufficient resistance to other wear stresses, inparticular to friction wear stresses. Their advantage lies essentiallyin scratch protection for relatively soft plastic components and in thetransparency of the films, so that the coating is also a possibility foroptical applications.

Amorphous carbon films exhibit outstanding wear protection propertieswith high hardness. They also exhibit low coefficients of friction insliding wear tests. These films cannot yet, however, be applied atdeposition rates on the same order of magnitude as those known fromplasma polymerization.

Metal-containing carbon films, e.g. i-C(WC), also offer good frictionaland vibratory wear protection, but because the deposition rate is againmuch lower than in the case of a plasma polymer coating process, and thelevel of thermal stress is high, they can be applied to only a few(usually expensive) types of plastic. In addition, protection againstimpact wear stress would require particularly thick film systems,precisely adjusted in terms of modulus of elasticity, that cannot beapplied onto ordinary types of plastic by pure carbon coating.

The deposition of hardness-gradient films is possible in carbon systems,but cannot be adapted to very soft substrates, in particular toplastics, since the very soft, graphite-like carbon films necessary forthe purpose have insufficient mechanical load-carrying capability at thebase of the film, i.e. exhibit poor adhesion under normal and shearloads.

SUMMARY OF THE INVENTION

It has now been found that, surprisingly, it is possible to join certainhard-material films, in particular those based on metal-containing andmetal-free carbon, in immovable and permanent fashion to surfaces ofsoft materials, in particular plastic surfaces, by way of a plasmapolymer support film having defined hardness and elasticity properties.The materials coated according to the present invention withhard-material films exhibit advantageous wear properties.

The surface film—for example a carbon film that can be ofmetal-containing or metal-free configuration—predominantly determinesthe frictional, vibrational, and abrasive wear protection of thecombination film, while the support film influences the impact wearprotection of the film package, so that overall, very good protection isachieved against frictional and fatigue wear even on components subjectto high levels of tribological stress. The surface films of theprotective coatings according to the present invention have a very goodaffinity for lubricants because of their carbon content, so thatlubrication film detachment is largely avoided. In addition, carbonfilms exhibit dry lubrication properties, i.e. film abrasion can producea kind of lubricating bushing on the tribological partner. They can alsobe varied in terms of their topography (particle size, surfaceroughness, porosity) in such a way that on the one hand very goodresistance to cavitation wear is achieved, and seizing of slidingsurfaces is also prevented.

The use of the plasma polymer film in this multi-level filmconfiguration makes it possible to adapt hardness and elasticity modulibetween the substrate and wear protection film, which results in higherductility and very good adhesion of the films even on soft plastics.

The high deposition rates possible with the plasma polymer process allowshort process times, which in turn permit a greater unit throughput fora given basic capital cost. This means that amortization of the capitalinvestment is distributed over more components, thus reducing theper-unit cost.

With the use of plasma polymer support films it is thus possible to workeconomically and at relatively low coating temperatures. Because of thecoating costs associated with them, this is particularly important formass-produced components, e.g. the plastic gears of actuating geardrives or electric tool drives.

The combination wear protection film according to the present inventionfor components made of substrates susceptible to wear, in particular ofplastics or soft metals, comprises a wear-resistant surface film and asupport film, located between substrate and surface film, that providesa transition over its thickness from the relatively soft base level ofthe support film resting on the substrate to properties of the surfacefilm. The surface film contains one or more of the elements carbon,nitrogen, silicon, or boron, the proportion of the carbon, nitrogen, orboron—or, if more than one of these elements is present, the sum of theproportions of these elements—is at least 30% by atomic weight,preferably at least 40% by atomic weight; and that the support film ismade of a plasma polymer that has been deposited from a silicon-organiccompound and/or an aliphatic and/or an aromatic carbon compound; andthat the support film exhibits a quasi-continuous transition in modulusof elasticity and optionally in hardness from the value of the base filmto the value of the surface film.

A “quasi-continuous transition” for the purposes of the presentinvention means either that the modulus of elasticity and/or thehardness of the film forms a gradient that can be represented as acontinuous curve, such that this curve need not have the same slope atall points but must not exhibit any discontinuity points relevant tostrength (i.e. no substantial breaks); or that a multi-step transitionfrom the soft base to the hard surface film is generated by way of apackage made up of a plurality of individual films whose modulus ofelasticity and/or hardness changes slightly and in directed fashion fromone film to the next.

The composition of the surface film is selected so that it is hardand/or possesses friction-reducing and/or dry lubricating properties,and protects the substrate from mechanical wear.

The films and film levels can contain further elements, preferablyhydrogen, oxygen, and metals, in addition to the aforesaid elements.

In the surface film in particular, metal dopants can be used to modifythe film properties and thus for optimal adaptation to the intended areaof application.

Preferably the surface film is made entirely or predominantly, inparticular at a proportion of more than 60% by atomic weight, of carbon,and at a proportion of up to 40% by atomic weight of nitrogen, boron,silicon, and/or metals. Surface films that contain more than 75% byatomic weight, in particular more than 85% by atomic weight, of carbonare particularly preferred.

Also particularly preferred are surface films that contain at least 60%by atomic weight carbon in combination with at leas 2% by atomic weight,preferably at least 10% by atomic weight, in particular at least 20% byatomic weight of one of the aforesaid elements, nitrogen, silicon,boron, or metals.

The properties of the protective films according to the presentinvention that are so valuable in terms of application engineeringresult from the interaction of the mechanical properties of the supportfilm and surface film, which in turn are based on their physicalcomposition and the structure that is created under the depositionconditions.

The plasma polymer films of the wear protection films according to thepresent invention are made of highly crosslinked polymer compounds thatexhibit a more or less statistical structure, meaning that in them, theatoms participating in their configuration do not, as in simple monomersor polymers, need to have a simple integral correlation with oneanother. Fractional and mutually independent atomic indices, such asSiC_(1.9)N_(0.3)B_(1.1), may therefore appear in the empirical formulae.This has the great advantage that it is possible to adjust thestoichiometric composition of the polymer film as required in thevarious levels, and to modify it as desired over the film thickness,either continuously or in small steps that do not impair strength.

The components including nitrogen, boron, silicon, and metals form, withthe carbon and among themselves, compositions in which all the phasespossible under the film formation conditions can be present. Forexample, nitrogen, boron, and silicon can be partially incorporated intothe three-dimensionally crosslinked structure of the plasma polymer, orcan be present, for example, as nitride or carbide phases or as mixedphases thereof.

Depending on the deposition conditions, metals can also be incorporatedinto the polymer or can be present as nitride, carbide, or boridephases, but also in unbound form.

In view of the large number of structures that are possible in theindividual levels of the support film and the surface film, a personskilled in the art could not have predicted the outstanding propertiesof the wear protection films according to the present invention.

All metals, with the exception of the first main group of the periodicsystem, are in principle suitable for modification of, in particular,the surface film properties. Advantageously, metals of the second tofifth periods of main group 3, the metals of the fourth through sixthmain groups, and the adjacent group metals, are used. Metals of theadjacent groups, in particular those of the fourth period, arepreferred. Tantalum, titanium, tungsten, and chromium are particularlypreferred.

Suitable metal compounds are, in particular, metal carbides, and/ornitrides and/or carbonitrides and/or borides and/or boronitrides of theaforementioned metals. The proportion of metal atoms and/or metalcompounds, in terms of metal, in the surface film is up to 40% by atomicweight. Preferably it is in the range from 1 to 30% by atomic weight, inparticular from 5 to 30% by atomic weight.

The plasma polymer support film also can contain metal atoms or metalcompounds, in particular if it is advantageous for adaptation of itsphysical data to those of the surface film. The base level of thesupport film advantageously is made of a plasma polymer that exhibitshigh adhesion to the material of the substrate. This can be achieved,for example, by the fact that the base level of the support film is madeof a plasma polymer that exhibits, in terms of its modulus ofelasticity, hardness, and deformability, a coordination with thematerial of the substrate that is sufficient to attain good adhesion.

In order to achieve particularly good adhesion properties between thesupport film and the relatively soft substrate, it has provenadvantageous for the base level of the support film to be made of aplasma polymer whose stoichiometric composition differs only slightlyfrom the stoichiometric composition of the monomer being delivered.Preferably the base level of the support film is made from a plasmapolymer of a silicon-organic compound.

Further criteria that promote good adhesion between the substrate andthe base level of the support film include the fact that the base levelof the support film is made of a plasma polymer that has functionalgroups identical or similar to the material of the substrate, or whosefunctional groups can interact with substituents on the substratesurface. If a soft metal is to be coated according to the presentinvention, it is advantageous if the base level of the support film ismade of a plasma polymer that contains polar groups with an affinity formetal. It is of course also possible to apply, between the surface ofthe substrate and the base level of the support film, an additionaladhesion-promoting film made of a material that has an affinity bothwith the substrate and with the material of the base level of thesupport film. An adhesion-promoting film of this kind advantageously hasa thickness of 5 to 100 nm, preferably 10 to 50 nm.

In order to achieve particularly good wear protection properties in thesurface film, it is advantageous for the support film to have, at leastin a film level region directly below the surface film, a gradient inits stoichiometric composition that terminates in the stoichiometriccomposition of the surface film, since this generally results in asmooth transition in elasticity properties from the support film to thesurface film.

For example, in the case of a surface film according to the presentinvention having a carbon surface film, an elastic, firmly adheringsupport film can be achieved by the fact that the carbon content,proceeding from the base level, increases with increasing film thicknessup to that of the surface film. The transition from the stoichiometryand modulus of elasticity of the plasma polymer film to that of thecarbon film is thus smooth or takes place in a plurality of small steps.

For example, the film base is made of a Si—C plasma polymer or a Si—C—Oplasma polymer; this is followed by a carbon gradient that continues tothe carbon surface film. Of course the total content of the other filmconstituents then constitutes a gradient opposite to the carbon content,since the sum of all the constituents must always add up to 100%.

The most important criterion for a good wear protection film accordingto the present invention is the quasi-continuous transition inelasticity data (and optionally in hardness data) from the base level ofthe support film to the surface film. This transition need notnecessarily be brought about by a continuous transition in carboncontent or in the content of another individual film constituentextending from the base level to the surface film. It is also possiblefor several of the film constituents, for example carbon, oxygen,nitrogen, or boron, to exhibit content gradients running in the samedirection, if the remaining constituents result in their totality in anopposite content gradient of equal magnitude. It is also possible—andparticularly advantageous depending on the composition of the base leveland of the surface film—to implement the continuous transition inelasticity properties from the base level to the surface film by way ofa sequence of concentration gradients of different film constituents indifferent film level regions. Examples of such stepped content gradientsare the following film structures:

The base level is constituted by a Si—C—O plasma polymer that isfollowed by an oxygen gradient. Adjoining this is a transition to a highnitrogen content, and following that, via a carbon gradient, is thecarbon surface film.

In another embodiment, the base level of the support film comprises aSi—C—N plasma polymer and transitions in a gradient to a high nitrogencontent; succeeding this is a transition to a high carbon content thatends in a carbon surface film.

In a further embodiment, the base level is made of a Si—C—O plasmapolymer or a Si—C—N plasma polymer; this is followed by a gradient withnitrogen or boron that transitions into a boron nitride or Si—N—Bsurface film with or without carbon. As already described above, allthese variants can contain metal atoms or metal compounds, for exampleTiN, in the support film but in particular in the surface film.

Doping with Si, B, N, O, or any desired metal atoms in a carbon surfacefilm is also possible.

The wear protection films according to the present invention areproduced by conventional methods of plasma. If desired, a PVD depositionoperation, for example using a sputtering process, can also be performedsimultaneously or subsequently. According to the present invention,plasma polymerization is performed in such a way that, optionally afterapplication of an adhesion-promoting film or after plasma finishcleaning (plasma etching) and/or plasma activation of the substratesurface, a monomer gas or a monomer gas mixture, comprising one or moregaseous silicon-organic compounds and/or aliphatic and/or aromaticcarbon compounds, and optionally further compounds containing dopingelements, is delivered to the plasma, resulting in plasma-induceddeposition onto the substrate of a polymer film that becomescrosslinked. The polymerization conditions and the monomer gascomposition are advantageously selected, on the basis of a predeterminedprogram identified in preliminary tests, in such a way that in each filmlevel produced in the structure of the film, the stoichiometriccomposition provided therefor is achieved.

In many it is advantageous to select the polymerization conditions atthe beginning of the deposition process in such a way that the soft filmbase approaches, in its stoichiometry, that of the monomer that is used.

All compounds with sufficient vapor pressure at temperatures between 20and 200° C. are in principle suitable for building up the plasma polymerfilms; vapor pressures of approximately 10 to 0.001 mbar are to beregarded as sufficient.

Organosilicon compounds, including those containing oxygen, nitrogen, orboron, are generally preferred as monomers for building up the wearprotection film according to the present invention. Suitable compoundsof this kind are found in the class of the poly(organosilanes),poly(siloxanes), poly(carbosilanes), poly(organosilazanes), andpoly(carbosilazanes). Examples of such monomers aretetramethylmonosilane, tetraethylmonosilane, methyldiphenylmonosilane,trimethylmonosilanol, diethyoxydimethylmonosilane, orhexamethylcyclotrisiloxane. Particularly preferred as the monomermaterial containing silicon are representatives of thepoly(organosilanes) and poly(siloxanes), in particularhexamethyldisilane (HMDS), hexamethyldisiloxane (HMDSO),tetraethylorthosilicate (TEOS), and divinyltetramethyldisiloxane (VSi₂).

Monomer gases suitable for the deposition of C—H films are saturated orunsaturated, branched or unbranched aliphatic hydrocarbons,advantageously those with 1 to 8, preferably with 1 to 4 carbon atoms,or aromatic hydrocarbons, preferably with 6 to 14 carbon atoms. Examplesof suitable hydrocarbons are alkanes, e.g. methane, ethane, propane,butane, isobutane, octane, isooctane; alkenes, e.g. ethene, propene;alkynes, e.g. acetylene; and aromatics, e.g. benzene, toluene, xylene.Preferred hydrocarbons are methane, ethane, and acetylene.

If elements other than C, H, and Si are to be incorporated into theplasma polymer, it is possible in principle to use monomers based on theaforementioned classes that contain these additional elements assubstituents or as chain members. For cost reasons, however, it is muchmore advantageous to incorporate these elements statistically into theplasma polymer, once it has been produced, by adding simple gasifiablecompounds of these elements to the gas flow that is delivered to theplasma. For example, oxygen and nitrogen can be introduced into thepolymer by adding oxygen, nitrogen, ammonia, or nitrous oxide. Gradualadaptation of the stoichiometry of the support film to a carbon surfacefilm can be accomplished, for example, by adding carbon-containingadditional gases, for example methane, ethylene, or acetylene, to themonomer gas flow. Also suitable for incorporating other elements intothe polymer and implementing the content gradients are, besides oxygen,nitrogen, ammonia, methane, ethylene, or acetylene, boron compounds suchas boric acid esters, boranols, or boranes, and nitrogen in the form ofcompounds containing amino or amido groups, for example acrylonitrile,and oxygen in the form of water, or mixtures of the aforesaidsubstances, as well as gasifiable metal compounds, preferably from theseries of lower metal alkoxides such as aluminum, zirconium, andtitanium alkoxides, for example zirconium(IV) tert-butoxide,titanium(IV) tert-butoxide, aluminum triethoxide, and from the series ofmetal carbonyls, for example tungsten hexacarbonyl.

It is particularly advantageous, however, to achieve metallic andnonmetallic dopants in the wear protection film according to the presentinvention by way of a PVD deposition operation occurring concurrentlywith the plasma polymerization process or performed subsequent thereto,for which a sputtering process, for example magnetron sputtering, pulsedmagnetron sputtering, DC sputtering, high-frequency sputtering, orhollow cathode gas-flux sputtering can be used.

Any metallic, nonmetallic, oxide, boride, carbide, silicide, or nitridetarget materials can be used in this situation.

The structure and composition of the wear protection films according tothe present invention and their levels can be controlled not only by thenature and quantitative relationships of the monomer gases, but also bythe process conditions. For example it is also possible, via a smoothchange in the process conditions toward a higher carbon content, toachieve a continuous transition from the composition and structure of abase level to a carbon surface film. Process conditions that can bedefined in order to control the thickness, structure, and composition ofthe film levels are the overall process pressure; the monomer partialpressure; the flow velocity of the gas mixture and, associatedtherewith, the monomer flow rate; the temperature of the gas mixture andsubstrate; the spacings and geometry of the gas inlet, plasma region,and substrate; the plasma energy and excitation frequency; and thecoating time. The plasma energy, working temperatures, substratespacing, and pressure conditions offer particularly effectiveopportunities for influencing the film structure. For example, elevatingthe plasma energy and the substrate temperature results in harderpolymer deposits; elevating the process pressure results in softerdeposits with less thickness. Selection of the spacing between plasmaand substrate, the concentration of oxygen or reactive gas in the gasmixture, the plasma power, and the substrate temperature can also beused to establish a desired topography for the polymer films, inparticular the surface film. Lowering the proportion of oxygen orreactive gas, the plasma power, and the substrate temperature, andelevating the substrate spacing from the plasma, each result in acoarsening of the film surface, and vice versa. If other conditions arekept constant, an elevation in plasma energy also results in polymerfilms with greater chemical resistance. It is normal to work with anenergy input of 100 to 6000 W, preferably 200 to 1000 W, to establishthe working pressure at values between 5 and 0.01 mbar, preferably 1 to0.025 mbar, and to establish the substrate temperature at between 20 and200° C., preferably between 20 and 120° C.

To assist film deposition, a bias voltage can be applied, capacitativelyor by direct contact, to the substrate. The bias voltage can be operatedin a pulsed or unpulsed fashion; in the pulsed case, monopolar orbipolar pulsing is possible. The pulse frequency can be varied withinwide limits. It is advantageous to select a pulse frequency between 1kHz and 100 MHz, preferably between 20 kHz and 50 MHz, in particularbetween 50 kHz and 20 MHz. For design-related reasons, pulse frequenciesbelow 27 MHz, e.g. a radio frequency of 13.56 MHz, are advantageous.

The monomer compositions and process parameters necessary for thedeposition of a polymer film with a specific stoichiometry, physicalproperties, and topography are ascertained on the basis of series ofpreliminary tests. These involve systematically performing plasmapolymerization tests with various monomers and monomer compositions anddifferent process parameters, and measuring the stoichiometric andphysical data of the polymer deposits thereby obtained. This yields theproperties of the polymer films for each monomer combination as afunction of the process parameters; these can be represented, forexample, in the form of calibration curves from which can be derived thecontrol program for the process conditions necessary for creating aplasma polymer film having, for example, a specific elasticity gradient.

The stoichiometric composition of the plasma polymer films can beascertained in known fashion by XPS analysis. Determination of thehardness and elasticity can also be accomplished using known methods:hardness determination is accomplished, for example, using the methoddescribed in P. Plein, “Plasmapolymerisation” (1989), pp. 112-114, inwhich the force that must be exerted on a diamond tip in order toproduce a scratch on the test surface serves as the measured variablethat allows, by way of calibration measurements, a determination of thehardness of the surface under test. The method is relatively imprecise,but when performed under conditions that are kept as constant aspossible has the accuracy necessary for the preliminary tests to beperformed here. The elasticity determination can be performed using ameasurement method also cited in P. Plein, “Plasmapolymerisation”(1989), pp. 108-110 and disclosed by K. Taube (seminar presentation ofNov. 25, 1987, Philips Research Laboratory, Hamburg, “Measuring theMechanical Properties of Thin Films”). In this, a diamond tip is appliedonto the film with a force such that it penetrates to a certain depth(not more than 20% of the film thickness), but does not produce anyplastic deformation of the surface. The application force is thenmodulated in a sine-wave pattern and the corresponding changes inpenetration depth are measured.

The values for penetration depth and change in force can be used tocalculate the modulus of elasticity.

The plasma necessary for generating the wear protection film accordingto the present invention can be a pulsed or unpulsed microwave plasmawith or without magnetic field support (ECR), or a plasma excited byhigh or medium frequency, in particular radio frequency (e.g. 13.56MHz), or created by hollow cathode excitation. The use of a microwaveplasma is particularly preferred, since it allows the highest depositionrates to be achieved. The method of pulsed or unpulsed magnetronsputtering is particularly suitable for implementing a simultaneous orsubsequent sputtering process. The present invention furthermore relatesto the objects equipped with a wear protection film according to thepresent invention; and the use thereof as components in technicaldevices, in particular in mechanical energy transfer mechanisms.

The exemplary embodiments below illustrate the manner in which wearprotection films according to the present invention are produced.

EXEMPLARY EMBODIMENTS Example 1

In a vacuum vessel with a microwave source and an adjustable androtatable substrate holder, a drive gear made of polyetheretherketone(PEEK), whose surface had been cleaned by plasma etching with oxygen (30sec at 600 W microwave power and 100 sccm oxygen flow) was coated in theregion of the teeth, while continuously rotating, under the followingconditions:

After the admission of 400 sccm gaseous HMDS(O), a plasma was ignitedwith 500 W microwave power. After a polymerization time of 10 minutes,the HMDS(O) portion in the gas flow was reduced uniformly to zero over a5-minute period, and over the same period acetylene was introduced intothe gas flow, uniformly increasing from 0 to 100% by volume. During thisperiod, the microwave power was increased from 600 to 800 W. Aftercompletion of the monomer gas concentration modification program,polymerization was continued for a further 10 minutes at the final flowrate of 200 sccm acetylene.

The gear coated according to the present invention was then removed fromthe vessel. It had in the region of the teeth a wear protection coatingaccording to the present invention 16 μm thick, comprising a supportfilm and, deposited thereon, a very hard, nonporous carbon surface film.

The support film had in the base level a carbon content of 30% by atomicweight, a silicon content of 40% by atomic weight, an oxygen content of20% by atomic weight, and a hydrogen content of 10% by atomic weight.Measured over its thickness, it had a positive carbon content gradientthat culminated in the surface film's carbon content of 90% by atomicweight. The protective film according to the present invention exhibitedoutstanding resistance to frictional, vibrational, and abrasive wear andto impact wear. It was moreover very hard and accordingly scratchproof,and exhibited a good affinity for lubricants.

Example 2

Example 1 was repeated, with the difference that during the period aftercompletion of the monomer gas concentration modification program andduring the continued plasma polymerization using 100% by atomic volumeacetylene, a PVD deposition operation was simultaneously performed usinga titanium target.

The resulting protective film according to the present inventioncontained, in the surface film, 10% by atomic weight titanium in theform of i-C(Ti). It exhibited even slightly greater resistance toabrasion, and a much higher resistance to frictional wear, than the filmproduced in Example 1.

What is claimed is:
 1. A combination wear protection film for acomponent made of a substrate susceptible to wear, the substrateincluding one of plastic and soft metal, the combination wear protectionfilm comprising: a wear-resistant surface film containing at least oneof carbon, nitrogen, silicon and boron, the at least one of carbon,nitrogen, and boron being at least 30% by atomic weight of the surface;and a support film positioned between the substrate and the surfacefilm, the support film having a thickness and providing a transitionover the thickness from a relatively soft base level of the support filmresting on the substrate to properties of the surface film, the supportfilm being made of a plasma polymer deposited from at least one of asilicon-organic compound, an aliphatic carbon compound and an aromaticcarbon compound, the support film having a quasi-continuous transitionin modulus of elasticity from a first value of the base level of thesupport film to a second value of the surface film.
 2. The combinationwear protection film according to claim 1, wherein the support filmexhibits a quasi-continuous transition in modulus of hardness from ahardness value of the base level of the support film to a hardness valueof the surface film.
 3. The combination wear protection film accordingto claim 1, wherein the at least one of carbon, nitrogen, silicon andboron is at least 40% by atomic weight of the surface film.
 4. Thecombination wear protection film according to claim 1, wherein thesurface film contains at least one of hydrogen, oxygen, and metals. 5.The combination wear protection film according to claim 1, wherein thesurface film contains more than 60% by atomic weight of carbon and up to40% by atomic weight of at least one of nitrogen, boron, silicon andmetals.
 6. The combination wear protection film according to claim 1,wherein the base level of the support film is made of a plasma polymerexhibiting high adhesion to a material of the substrate.
 7. Thecombination wear protection film according to claim 1, furthercomprising: an adhesion-promoting film positioned between a surface ofthe substrate and the base level of the support film.
 8. The combinationwear protection film according to claim 1, wherein at least in a filmlevel region directly below the surface film, the support film exhibitsa gradient in a stoichiometric composition that terminates in astoichiometric composition of the surface film.
 9. A method forproducing a wear protection film by plasma polymerization, comprising:providing a substrate composed of one of plastic and a soft metal; anddelivering one of a monomer gas and a monomer gas mixture to a plasma,the one of the monomer gas and the monomer gas mixture including atleast one of i) at least one gaseous silicon-organic compound, ii) analiphatic carbon compound, and iii) an aromatic carbon compound toproduce a film on the substrate by plasma polymerization.
 10. The methodaccording to claim 9, further comprising: performing the delivering stepafter one of i) applying an adhesion-promoting film to the substrate,ii) plasma etching the substrate, and iii) plasma activating a surfaceof the substrate.
 11. The method according to claim 9, wherein thedelivering step further includes delivering doping elements to theplasma.
 12. The method according to claim 9, wherein the delivering stepis performed simultaneously with a PVD deposition operation.
 13. Themethod according to claim 9, wherein after the delivering step,performing a PVD deposition operation.
 14. The method according to claim9, further comprising the step of: applying one of a pulsed bias voltageand an unpulsed bias voltage to the substrate to assist film deposition,the bias voltage being applied one of capacitively and by directcontact.
 15. The method according to claim 9, further comprising thestep of: producing metallic and nonmetallic dopants of the film via aPVD deposition operation performed one of concurrently with the plasmapolymerization and subsequently with the plasma polymerization.
 16. Themethod according to claim 9, further comprising the step of: producingmetallic and nonmetallic dopants of the film via a PVD depositionoperation performed subsequently to the plasma polymerization.
 17. Themethod according to claim 9, further comprising the step of: providing asupport film, made of a plasma polymer, between the substrate and thefilm, the support film having a thickness and providing a transitionover the thickness from a relatively soft base level of the support filmresting on the substrate to properties of the film, by depositing atleast one of a silicon-organic compound, an aliphatic compound and anaromatic carbon compound, the support film having a quasi-continuoustransition in modulus of elasticity from a first value of the base levelof the support film to a second value of the film.
 18. The methodaccording to claim 17, further comprising the step of: producingmetallic and nonmetallic dopants of the film via a PVD depositionoperation performed subsequently to the plasma polymerization.
 19. Acomponent, comprising: a material susceptible to wear; a wear-resistantsurface film containing at least one of carbon, nitrogen, silicon andboron, the at least one of the carbon, nitrogen, silicon and boron beingat least 30% by atomic weight of the film; and a support film positionedbetween the material and the protective film, the support film having athickness and providing a transition over the thickness from arelatively soft base level of the support film resting on the materialto properties of the surface film, the support film being made of aplasma polymer deposited from at least one of a silicon-organiccompound, an aliphatic compound and an aromatic carbon compound, thesupport film having a quasi-continuous transition in modulus ofelasticity from a first value of the base level of the support film to asecond value of the surface film.
 20. The component according to claim19, wherein the component is a technical device that includes amechanical energy transfer mechanism.